The present invention pertains to the protection of the prosthetic knee devices between the femoral condyles and the tibial plateau during surgical implantation.
Over time, and with injury or overuse, cartilage breaks down. Unfortunately, cartilage has relatively little capacity for repair. As it breaks down the body's natural healing response is activated; however, instead of healing, chronic inflammation occurs. This inflammation in turn causes pain, which is better known as arthritis. Once arthritis sets in, a person is susceptible to chronic pain. When the degeneration of the cartilage progresses beyond a tolerable level of pain the joint can be replaced with a prosthesis. A joint prosthesis replaces the degenerated bone and cartilage with artificial components, generally made of metals, ceramics, plastics and/or elastomers.
Knee prosthetic devices can be divided into several types, the most common of which is called a total knee arthorplasty. In this procedure, a portion of the femur (femoral condyles) and an adjacent portion of the tibia (the tibial plateau) are resected or removed and replaced by prosthetic components, with a polyethylene insert bearing substituted for the original meniscal cartilage.
Generally the tibial prosthetic component is first inserted and secured with an appropriate cement, adhesive and/or fastening element. Then the femoral prosthetic component is normally inserted and secured. At this stage it is necessary not to scratch, scar, otherwise damage, or move either one of the polished prosthetic components until the cement curing phase of the surgery is completed. This is normally accomplished by having the assistant apply traction between the femur and the tibia while the leg is in a 90 degree position. A common alternative method of distraction is utilizing the smallest size trial insert bearing (prosthetic meniscus) as a buffer. Even the use of the smallest bearing trial insert (prosthetic meniscus) can be too tight causing the uncured cemented prosthesis to move and malposition.
Unfortunately, even with the greatest care, scratching or marring of the polished component surfaces nevertheless can occur. Even a minor scar or scratch will eventually cause premature wear and ultimately prosthetic failure. If the scratching or marring is major, the knee prosthesis must be completely removed requiring the patient to have additional surgery and to be subjected to additional prolonged pain and stress.
In addition, when a prosthetic meniscus is inserted between the prosthetic knee components, this is generally accomplished by first inserting retractors between the prosthetic components for assisting in placement or insertion of the meniscus between the prosthetic components. When inserting the retractors, there exists once again a very great risk that the retractors will scratch, mar or malposition the uncured cemented polished components.